Complexity of Learning: J. Stephen Judd

Learning is a quintessential ability of brains, and it is a major focus of much
connectionist research. Unfortunately, the learning algorithms reported in the literature so far are all unacceptably slow in large networks. Although it is clear that
we need to be able to scale up our applications to much bigger networks, it is not
at all clear how to achieve this. Many researchers view this as the most pressing
challenge for current connectionist research.